Liggins Institute, The University of Auckland , Auckland , New Zealand.
Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado.
J Appl Physiol (1985). 2018 Mar 1;124(3):717-728. doi: 10.1152/japplphysiol.00803.2017. Epub 2017 Nov 9.
Muscle disuse results in the loss of muscular strength and size, due to an imbalance between protein synthesis (MPS) and breakdown (MPB). Protein ingestion stimulates MPS, although it is not established if protein is able to attenuate muscle loss with immobilization (IM) or influence the recovery consisting of ambulatory movement followed by resistance training (RT). Thirty men (49.9 ± 0.6 yr) underwent 14 days of unilateral leg IM, 14 days of ambulatory recovery (AR), and a further six RT sessions over 14 days. Participants were randomized to consume an additional 20 g of dairy protein or placebo with a meal during the intervention. Isometric knee extension strength was reduced following IM (-24.7 ± 2.7%), partially recovered with AR (-8.6 ± 2.6%), and fully recovered after RT (-0.6 ± 3.4%), with no effect of supplementation. Thigh muscle cross-sectional area decreased with IM (-4.1 ± 0.5%), partially recovered with AR (-2.1 ± 0.5%), and increased above baseline with RT (+2.2 ± 0.5%), with no treatment effect. Myofibrillar MPS, measured using deuterated water, was unaltered by IM, with no effect of protein. During AR, MPS was increased only with protein supplementation. Protein supplementation did not attenuate the loss of muscle size and function with disuse or potentiate recovery but enhanced myofibrillar MPS during AR. NEW & NOTEWORTHY Twenty grams of daily protein supplementation does not attenuate the loss of muscle size and function induced by 2 wk of muscle disuse or potentiate recovery in middle-age men. Average mitochondrial but not myofibrillar muscle protein synthesis was attenuated during immobilization with no effect of supplementation. Protein supplementation increased myofibrillar protein synthesis during a 2-wk period of ambulatory recovery following disuse but without group differences in phenotype recovery.
肌肉废用会导致肌肉力量和大小的丧失，这是由于蛋白质合成 (MPS) 和分解 (MPB) 之间的失衡造成的。蛋白质摄入会刺激 MPS，尽管目前尚不清楚蛋白质是否能够在固定不动（IM）时减轻肌肉损失，或者是否会影响由步行运动和随后的抗阻训练（RT）组成的恢复过程。三十名男性（49.9 ± 0.6 岁）接受了 14 天的单侧腿部 IM、14 天的步行恢复期（AR）和另外 14 天的 6 次 RT 训练。参与者在干预期间随机摄入额外的 20 克乳制品蛋白质或安慰剂。IM 后等长膝关节伸展力量降低（-24.7 ± 2.7%），AR 部分恢复（-8.6 ± 2.6%），RT 后完全恢复（-0.6 ± 3.4%），补充剂无影响。股四头肌横截面积在 IM 后减少（-4.1 ± 0.5%），AR 部分恢复（-2.1 ± 0.5%），RT 后增加至基线以上（+2.2 ± 0.5%），无治疗效果。使用氘水测量的肌原纤维 MPS 不受 IM 影响，蛋白质也无影响。在 AR 期间，仅在补充蛋白质时 MPS 增加。蛋白质补充剂不能减轻肌肉失用引起的肌肉大小和功能的丧失，也不能促进恢复，但在 AR 期间增强了肌原纤维 MPS。新内容和值得注意的内容：每天 20 克蛋白质补充剂不能减轻 2 周肌肉失用引起的肌肉大小和功能的丧失，也不能促进中年男性的恢复。固定不动期间，平均线粒体但不是肌原纤维肌肉蛋白质合成减少，补充剂无影响。蛋白质补充剂在停用后 2 周的步行恢复期内增加了肌原纤维蛋白合成，但在表型恢复方面没有组间差异。
